Gluconeogenesis

Question 1

What is Gluconeogenesis?

Answer 1

It is the synthesis of new glucose from non carbohydrate sources

Question 2

Where does Gluconeogenesis take place?

Answer 2

Takes place in the liver and a little in the kidneys

Question 3

Give some precursors of Gluconeogenesis

Answer 3

1. Lactate
2. glycerol
3. Amino acids

Question 4

What does Gluconeogenesis require/

Answer 4

Consumes ATP

Question 5

Is Gluconeogenesis the reverse of glycolysis?

Answer 5

NO

Question 6

Which steps does Gluconeogenesis need to by pass and what?

Answer 6

Needs to pass the 3 stages:
1. conversion of glucose into pyruvate
2. Glucose into Glucose-6-phosphate
3. Fructose-6-phosphate into Fructose1-6- bisphosphate
These 3 reach release the most energy in glycolysis so gluconogenesis needs to bypass these steps

Question 7

Go through the stages of Gluconeogenesis

Answer 7

1. Pyruvate into oxaloacetate
2. oxaloacetate into phosopoenol pyruvate
3. phosopoenol pyruvate into 2- phosphoglycerate
4. 2- phosphoglycerate into 3- phosphoglycerate
5. 3- phosphoglycerate into 1,2 biphoshpglycerate
6. 1,2 biphoshpglycerate into Glyceraldehyde 3 phosphate
7. Glyceraldehyde 3 phosphate into fructose 1,6 biphophate
8. fructose 1,6 biphophate into fructose 6 biphophate
   9 fructose 6 biphophate into glucose 6 phosphate
9. glucose 6 biphophate into glucose

Question 8

What does the first by pass step start with?

Answer 8

Starts with pyruvate

Question 9

How does the first by pass step occur?

Answer 9

1. Pyruvate dissolves into the mitochondria
2. It is converted into Oxaloacetate via Pyruvate
   carboxylase
3. Oxaloacetate is converted into malate via Malate
   dehydrogenase
4. Malate then leaves the mitochondria
5. Malate is converted in Oxaloacetate via Malate
   dehydrogenase
6. Oxaloacetate is converted into Phosphoenolpyruvate via Phosphoenolpyruvate carboxykinase

Question 10

What does Pyruvate

carboxylase do?

Answer 10

Converts pyruvate into Oxaloacetate this reaction releases ATP

Question 11

What does Malate

dehydrogenase do?

Answer 11

Converts Oxaloacetate into malate this reaction releases NAD+

Question 12

What does Malate

dehydrogenase do?

Answer 12

It concerts malate into Oxaloacetate this reaction releases NADH

Question 13

What does Phosphoenolpyruvate carboxykinase do?

Answer 13

Converts Oxaloacetate into Phosphoenolpyruvate

Question 14

After Phosphoenolpyruvate has formed what can happen to it?

Answer 14

1. It can either form 2-Phosphoglycerate

2. Can be re converted into pyruvate

Question 15

How is the conversion of Phosphoenolpyruvate into pyruvate stopped?

Answer 15

Excess glucagon prevents pyruvate kinase from working so pyruvate doesn’t form so glycogen isn’t broken down

Question 16

State the second step of glycolysis we need to bypass in Gluconeogenesis

Answer 16

We need to reverse the Conversion of Fructose
6-phosphate into Fructose
1,6-bisphosphate

Question 17

How is the conversion of Fructose
6-phosphate into Fructose
1,6-bisphosphate
reversed in Gluconeogenesis?

Answer 17

By the enzyme 1,6-bisphosphatase that converts Fructose
1, 6-biphosphate into Fructose
6 phosphate

Question 18

How is the conversion of Fructose
6-phosphate into Fructose
1,6-bisphosphate and its reverse controlled?

Answer 18

It is reciprocally controlled Via Fructose 2,6 biphosphate AMP and Citrate ATP H+
Citrate increases the effectiveness of Fructose
1,6-bisphosphatase so more fructose 6 phosphate made
Fructose 2,6 biphosphate AMP increases the effectiveness of Phosphofructo-kinase so increasing the production of Fructose 1,6-bisphosphate

Question 19

State the third step of glycolysis we need to bypass in Gluconeogenesis

Answer 19

We need to reverse he conversion of Glucose into glucose into glucose 6-phosphate

Question 20

How is the conversion of Glucose into glucose into glucose 6-phosphate reversed in Gluconeogenesis

Answer 20

Via the enzyme Glucose

6-phosphatase which converts glucose 6-phosphate into glucose

Question 21

What is Glucose 6-phosphatase dependent on>?

Answer 21

Magnesium

Question 22

During prolonged fasting how does our body get energy?

Answer 22

It breaks down our fat stored to release fatty acids ad glycerol backbone

Question 23

How are fatty acids used to obtain energy?

Answer 23

They undergo gluconeogenesis

Question 24

What happens to glycerol That is formed via the breakdown of fat stores?

Answer 24

1. Glycerol is converted into Glycerol Phosphate via glycerol kinase
2. Glycerol Phosphate is then converted into DHAP via NAD+ and glycerol phosphate
   dehydrogenase

Question 25

What does glycerol kinase do?

Answer 25

Breaks dow glycerol into glycerol kinase

Question 26

What does glycerol phosphate

dehydrogenase do?

Answer 26

Converts Glycerol Phosphate is then converted into DHAP

Question 27

When is lactate used as a glucose precursor?

Answer 27

During vigorous exercise lactate is
produced in anaerobic muscle and
by glycolysis in erythrocytes

Question 28

How can lactate be used as a glucose precursor

Answer 28

Lactate is converted into pyruvate via Lactate dehydrogenase

in the cytosol in the liver cells to produce NADH

Question 29

What does Lactate dehydrogenase do?

Answer 29

Converts lactate into pyruvate

Question 30

Give the overall conversion o pyruvate into glucose

Answer 30

2Pyruvate +4ATP +2GTP+ 2NADH+ 2H+ + 6H2O
->
Glucose + 2NAD+ + 4ADP +2GDP + 6Pi+ 6H+

Question 31

How man high energy phosphates are needed to convert pyruvate into glucose?

Answer 31

6

Question 32

State the over all free energy change of gluconeogenesis

Answer 32

-16kj/mol

Question 33

State the over all free energy change of glycolysis

Answer 33

at least -63kj/mol

Question 34

Can both glycolysis and gluconeogenesis occur at high rates simultaneously?

Answer 34

no as they are regulated allosterically and by covalent modification